PECOS, TEXAS -- For some small oil companies in West Texas, low crude prices are beginning to sting.

Green Century Resources, a private oil company in Midland, is weighing an investment in a drilling project that appeared profitable a few months ago when crude prices hovered above $50 a barrel. Now, with U.S. prices under the $45-a-barrel mark, the small company may have to hold off on its plans, said James Mayer, founder and chief executive of Green Century.

"If oil holds under $45, that would make a difference to us," Mayer said, adding his company is working to whittle down its projected capital and operating costs.

Several small operators in West Texas told the Houston Chronicle they're face increasing pressure from rising oil field service costs, particularly in hydraulic fracturing, in part because the downturn wiped out some of the service companies and allowed rivals to raise prices. That oil prices are falling now has convinced some to rethink their expansion plans for the year, which were set at a time when oil prices were higher.

"You can see even the difference in traffic out here in Midland," Mayer said. "You can feel it slowing down."

Larger, publicly traded oil producers in West Texas locked in higher prices for future output earlier this year, and so far, they haven't signaled plans to reduce drilling activity in the region.

Houston-based Noble Energy, for example, has amassed a large footprint in the Delaware Basin through two multibillion-dollar acquisitions, and it plans to expand its drilling fleet there later this year even if oil stays cheap, said Donnie Moore, vice president of the Noble's Marcellus and Texas business units, in an interview at the Houston firm's field offices near Pecos, Texas.

Nearly two-thirds of Noble's inventory of oil wells in the Delaware Basin breaks even around $40 a barrel, and the company plans to boost its U.S. onshore oil production 40 percent in the second half of 2017 compared to the same period last year, he added.

"We're really pushing forward," Moore said. "We'll always be looking at the market, and activity, and what's needed, but right now, we're still at five drilling rigs, two frac crews and we're planning a sixth rig later in the year."

But for smaller oil producers, cash flow determines drilling plans. Midland-based Fasken Oil & Ranch, a small producer in the Permian Basin, owns the mineral rights on its oil acreage in West Texas, which means it doesn't have to pay out royalties as its rivals do.

But even so, if oil prices don't bounce back soon, Fasken "will cut back pretty significantly," said Tommy Taylor, director of oil and gas development at Fasken.

"There is a huge difference between $40 oil and $50 oil," Taylor said. "If we don't have the cash flow, we don't do it."

U.S. oil prices edged lower on Tuesday, dipping 16 cents to $44.24 a barrel in early trading.